Corneal pannus (chronic superficial keratitis) in the German shepherd dog

Diagnosing Corneal Pigmentation in Small Animals

The transparency of the cornea is critical to its role in transmitting light. Loss of corneal transparency results in visual impairment. Corneal pigmentation results from melanin accumulation in the epithelial cells of the cornea. Differential diagnosis for corneal pigmentation include corneal sequestrum, corneal foreign body, limbal melanocytoma, iris prolapse, and dermoid. These conditions must be excluded to reach a diagnosis of corneal pigmentation. A myriad of ocular surface conditions are associated with corneal pigmentation, including qualitative and quantitative tear film deficiency, adnexal disease, corneal ulceration, and breed-related corneal pigmentation syndromes. Accurate etiologic diagnosis is critical to determining effective treatment.

Cyclosporine A Delivery Platform for Veterinary Ophthalmology—A New Concept for Advanced Ophthalmology

Cyclosporine A (CsA) is a selective and reversible immunosuppressant agent that is widely used as a medication for a wide spectrum of diseases in humans such as graft versus host disease, non-infectious uveitis, rheumatoid arthritis, psoriasis, and atopic dermatitis. Furthermore, the CsA is used to treat keratoconjunctivitis sicca, chronic superficial keratitis, immune-mediated keratitis and equine recurrent uveitis in animals. The selective activity of Cyclosporine A (CsA) was demonstrated to be an immunomodulation characteristic of T-lymphocyte proliferation and inhibits cytokine gene expression. Moreover, the lipophilic characteristics with poor bioavailability and low solubility in water, besides the side effects, force the need to develop new formulations and devices that will provide adequate penetration into the anterior and posterior segments of the eye. This review aims to summarize the effectiveness and safety of cyclosporine A delivery platforms in veterinary ophthalmology.

A study of the association between chronic superficial keratitis and polymorphisms in the upstream regulatory regions of DLA-DRB1, DLA-DQB1 and DLA-DQA1

Canine chronic superficial keratitis (CSK) is an inflammatory corneal disease that primarily occurs in German shepherd dogs (GSDs). Several studies support the hypothesis that CSK is an immune-mediated disease. To investigate the genetic factors associated with CSK development, the upstream regulatory regions (URRs) of the DLA-DRB, -DQA and -DQB genes were genotyped in 60 dogs, including 32 CSK animals. LD analysis identified two blocks (r(2)≤45), with two DLA-DRB1 and five DLA-DQB1 haplotypes. Analysis of DLA-URR alleles/haplotypes showed a significant association between DQB1*-154 [C/T] (p=0.016) and CSK, suggesting that the T variant may increase the risk for developing CSK disease (OR=3, 95% CI=1.25-7.68). When haplotype associations were performed, the URR-DQB*CATT haplotype was significantly associated with CSK (p=0.016), increasing the risk of develop this disease over two-fold (OR=3, 95%, CI=1.25-7.68). These results showed that dogs homozygous at DRB1*69 [C/T] had a risk for developing CSK disease that was over four times the risk for heterozygotes. This genetic association supports the previous clinical, histological and pharmacological studies that suggest that CSK is an immune-mediated disease, and this association could potentially be used to identify susceptible animals.

MHC class II risk haplotype associated with canine chronic superficial keratitis in German Shepherd dogs

Canine chronic superficial keratitis (CSK) is an inflammatory ocular disease of an autoimmune origin leading to blindness if untreated. The main symptoms of CSK are progressive, bilateral vascularisation, fibrous tissue formation and pigmentation of the anterior corneal stroma. Although CSK is found in many breeds it is most prevalent in German Shepherd dogs (GSDs). Since Major Histocompatibility Complex (MHC) class II is associated with several autoimmune diseases in dogs we investigated the possible role of DLA-DRB1, -DQA1 and -DQB1 in GSDs affected with CSK. Our study population included 25 healthy controls and 30 CSK dogs. Most of the affected dogs were females suggesting a female predisposition. We identified 11 unevenly distributed haplotypes of which DLA-DRB1*01501/DQA1*00601/DQB1*00301 was significantly associated with the CSK dogs (OR=2.67, CI=1.17-6.44, p=0.02). We also found that overall homozygosity of MHC class II increases risk for CSK (OR=4.37, CI=1.27-18.46, p=0.02) and homozygosity of the risk haplotype by over eight-fold (OR=8.5, 95% CI=1.4-224, p=0.017). This study identifies a MHC class II risk haplotype for CSK in GSD and further supports the autoimmune origin of the disease.

Immune-mediated canine and feline keratitis

Although the normal cornea is devoid of vasculature and lymphatics, there are still several immune-mediated corneal conditions that can occur in dogs and cats. An overview of corneal immunology is presented. Diseases of dogs, including chronic superficial keratitis, superficial punctate keratitis, and canine adenovirus endotheliitis, as well as feline diseases, including eosinophilic keratitis and herpesvirus-related conditions, are discussed.

Major histocompatibility class II expression in the normal canine cornea and in canine chronic superficial keratitis

OBJECTIVE

To compare the expression of major histocompatibility complex (MHC) class II antigen in the corneas of normal dogs and dogs affected with chronic superficial keratitis (CSK).

METHODS

MHC class II expression was determined in frozen sections of normal canine cornea and cornea from lesions of CSK by immunohistochemistry using a monoclonal antibody directed against the canine MHC class II molecule. Langerhans cell phenotype was determined morphologically and by histochemical determination of ATPase activity. To determine the influence of gamma interferon on expression of MHC class II molecules by corneal cells, corneal explants were cultured with the cytokine and MHC class II expression determined as above.

RESULTS

Numerous MHC class II-expressing cells were demonstrated within the stroma and epithelium of the normal corneal limbus and conjunctival epithelium while very little MHC class II expression was detected in the central region of normal canine cornea. In limbal and conjunctival epithelium, cells expressing MHC class II antigen showed ATPase activity, suggesting that they were Langerhans cells. Corneas from dogs with CSK showed MHC class II expression associated with stromal cells, some of which exhibited a dendritic morphology while most were lymphocytic. Corneal epithelial cells within the lesion also aberrantly expressed MHC class II. Corneal explants expressed MHC class II to varying degrees after differing periods of incubation with the cytokine gamma interferon.

CONCLUSIONS

While the normal central cornea has little MHC class II expression, aberrant expression occurs in CSK, associated with secretion of gamma interferon by infiltrating CD4-expressing lymphocytes. Although this change is likely to be a secondary feature of the CSK lesion, increased MHC class II expression may play a part in perpetuating the corneal inflammation seen in the disease.

Histological and immunohistochemical evaluation of canine chronic superficial keratitis

Chronic superficial keratitis (CSK) is an inflammatory disease of the canine cornea, characterised by infiltration of leucocytes into the anterior corneal stroma. The present study describes a quantitative histomorphometric analysis of the cell types infiltrating the corneal stroma in this disease. Infiltrating cells were quantified in samples taken at superficial keratectomy and processed for routine histology. Further characterisation of lymphocyte phenotypes was achieved by immunohistochemistry performed using a panel of monoclonal antibodies recognising canine lymphocyte CD antigens. Lymphocytes expressing the CD4 antigen were found to be the predominant infiltrating cell types in the CSK lesion. A significantly smaller number of lymphocytes expressed the CD8 antigen. The CD4/CD8 ratio was consistently above 2 and rose to above 4 at the advancing border of the lesion. A proportion of lymphocytes were shown by immunohistochemistry to contain gamma interferon. This study forms a basis for work further evaluating the cytological events central to the development of this spontaneous potentially auto-immune corneal disease.

Treatment of canine nictitans plasmacytic conjunctivitis with 0.2 per cent cyclosporin ointment

Nictitans plasmacytic conjunctivitis, commonly referred to as plasma cell infiltrate of the nictitans or plasmoma, was diagnosed in 12 dogs (23 eyes) on the basis of clinical signs and nictitans conjunctival biopsy specimens. These dogs underwent a clinical therapeutic trial with twice daily 0.2 per cent cyclosporin ophthalmic ointment. Response to therapy was monitored over a six-week period and repeat biopsy specimens were then taken. Significant (P < 0.05) reductions between pre- and post trial scores were recorded for: mucopurulent ocular discharge quantity; degree of bulbar conjunctival hyperaemia; areas of nictitans hyperaemia, thickening and depigmentation. Schirmer tear test values significantly increased between the start and end of treatment. Biopsy specimens were subjected to selective detection procedures for plasma cells (methyl green-pyronin staining) and T lymphocytes (CD3 antigen labelling). Mean cell counts showed a significant reduction in plasma cell numbers, but the trend towards reduced T lymphocyte numbers was not significant.

A report on drug-induced kerato-conjunctivitis sicca in dogs

Kerato-conjunctivitis sicca is reported in beagle dogs treated with an antispasmodic compound for 26 weeks during a routine toxicity study. There was a deficiency of lachrymal secretion associated with keratitis and corneal vascularization. Histopathologically, the changes were characterized by vascularization, fibroblast proliferation and infiltration of inflammatory cells in the substantia propria. In some cases, the inflammation also occurred in corneal epithelium, ocular conjunctiva and corneal limbi.